Treatment of synthetic filament



Patented Feb. 16, 1943 TREATMENT OF SYNTHETIC FILAMENT -Maurlce L. Maoht, Jersey City, and Malcolm M. Renfrew, Arlington, N. .L, assignors to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application July 22, 19-41, Serial No. 403,550

6 Claims.

This invention relates to filaments of superpolyamides and the like and, more particularly, to a method of using them as bristles in brushes.

The filaments in question are those made from synthetic fiber-forming polymeric amides commercially designated by the generic name nylon and made in accordance with United States Patents 2,071,250, 2,071,253, and 2,130,948. From substances of this class, filaments are formed by a process which comprises the steps of melting the substance and extruding the molten mass by means of pressure through a suitable orifice to form a continuous filament, and then subjecting the filament to cold-drawing. Filaments thus made, and particularly those of finished diameter between about 0.010 and about 0.020 inch, are in general commercialuse as bristles in brushes of various types, and particularly in tufted brushes such as toothbrushes and hairbrushes.

In setting bristles in the manufacture of such brushes, usually by the use of automatic machinery, several filaments are inserted together into each hole in the brush-back, to form what is known as a tuft. The brush is thus made up of a plurality of tufts, anchored in corresponding holes arranged, usually with geometrical regu-.

larity, over the area of the brush back. After all of the tufts have been inserted, it is customary to cut them to predetermined lengths, and also, particularly in the case of toothbrushes, to bevel each tuft to a tip of conical shape. These operations of trimming and finishing enhance both the appearance and the utility of the brushes.

When brushes are bristled in this general manner with natura1 bristles, particularly hog bristles, the individual bristles going to make up the tuft remain closely packed together and approximately parallel, to constitute a compact and orderly tuft, clearly separated from adjacent tufts, and adapted to be trimmed and beveled readily and neatly.

But with artificial filaments of the fiber-forming polymeric amides difiiculty has been encountered frequently, or even regularly, in that the individual filaments ofthe tuft tend to spread apart in random manner, so that the tuft, instead of being compact'and neat, is spreading and bushy. Obviously a brush composed of tufts of this character is inferior in appearance, in that the individual tufts tend to encroach upon each other, and also as a result of thedifficulty or impossibility of neatly trimming or beveling the top of a tuft of this loose, irregular character. And

. subsequent operations of correspondingly. theutility of the brush is impaired also.

A further difficulty arises in a failure of the bristles to feed smoothly into the picker which transfers a group of bristles from the hopper to the setting mechanism to form a tuft in the brush; the picker then fails to transfer asufilcient number of bristles to form a full tuft of normal; size, which will fil1 the loop of the anchoring wire which holds the bristles in the brush, and the result is an insecurely anchored tuft, from which the bristles are readily pulled out.

It is an object of the present invention to improve the behavior of filaments of fiber-forming polymeric amides in their application as bristles in brushes, and more particularly to make possible the formation therefrom, by ordinary bristling technique and with the use of ordinary bristling equipment, of full, straight, compact and neat tufts, whereby to effect economy 'in the finishing the brushes, and to enhance the appearance and utility thereof. Other objects of the invention will be apparent from the description given hereinafter.

These objects are accomplished in accordance with the present invention by coating the bristle of .a synthetic polymeric amide with one or a mixture of certain substances presently to be designated, this coating being achieved conveniently and preferably by bringing the bristle into contact with the said substance contained in a liquid vehicle, whereby to coat the filament, and thereafter evaporating the liquid from the surface of the filamen The invention further comprises the use of such filaments, so coated, in the process of bristling brushes by known methods, including the preferred use of automatic machinery therefor. and also filament so coated and brushes made therefrom.

The coating substances which are operative in accordance with the present invention include individuals and mixtures selected from the group comprising straight-chain aliphatic alcohols containing even numbers of carbon atoms between twelve and eighteen. Of the available members of this group, certain mixtures are pre ferred, but merely for reasons of commercial convenience.

Alcohols of this group are ordinarily not available commercially in completely isolated form; for the purposes of the present invention the ordinaryv commercial mixtures of homologues are satisfactory, provided that they do not contain more than small proportions of homologues below or above the-stated limits of 12 and is carbon The application of a coating of one or a mixture of substances from this group upon a bristling .filament of synthetic fiber-forming polymeric amide may be. accomplished by rubbing the dry substance upon the surface of the filament butit is preferred, for reasons of economy and ease in achieving thorough and uniform coating, to apply the coating substance in solution or dispersion in a liquid vehicle to the surface of the filament, soas to wet the latter there'- with, and then to remove the liquid vehicle from the surface of the filament by evaporation.

If the liquid vehicle used is a solvent for the coating substance and contact of the filament with the resulting sohition of the substance is complete, then this embodiment of the technique of the present invention results in an unbroken coating of the substance upon the filament.

If the liquid vehicle is one in which the coating substance is not soluble, the coating substance is finely dispersed therein and, in order to accomplish'the dispersion, and also to promote theuniform application of the resulting mixture to the filament, it is desirable to include in the liquid mixture a dispersing and wetting agent, such as a fatty alcohol sulfate. u I

As a solvent for coating substances of the group in question, hexane is ordinarily convenient and desirable, but obviously the selection may be made from other solvents, with due regard to the avoidance of a too rapid or a too slow rate ,of evaporation, and also of toxicity, high cost,

or other obviously objectionable characteristics. In general, none of .the solvents likely to be selected will have any solvent action upon the filament itself.

If the coating substance is to be applied in the form of a dispersion. the liquid vehicle selected the auxiliary substance ordinarily to be included for the purpose of effective dispersion and wetting, may be selected from the wide variety of "Lorol."-A mixture of straight-chain (nor- 'mal) alcohols of even numbers of carbon atoms from 8 to 18, inclusive, with lauryl alcohol .preponderating.

0-18 alcohol."-A mixture of alcohols of 16, 1'7 and, predominantly, 18 carbon atoms, derived from hydrogenated coconut oil esters; contains about 95% of'stearyl alcohol. T

Example I.A bristling filament composed of will ordinarily, but not necessarily, be water and polyhexamethylene adipamide and formed by extrusion and'cold-drawing, and having a diameter of 0.011 inch, is passed between felt covered pads, the surfaces of which carry a finely-divided mixture of-equal parts by welllht of 0-18 alcohol" and Iorol. This treatment serves to apply tothesurfaceofthefilamentacoating ofthis mixture. The filament is cut tolengths, bundled,

Parts by weight "0-18 alcohol 13 1 1.: Hexane 97.6

Through the resulting solution is passed a bristling filament composed of hexamethyiene adipamide, formed by extrusion and cold-drawing, and of diameter 0.011 inch. The filament,

wet with the solution, passes then through a bathof warm air, which serves to eifect the removal of the hexane by evaporation.

The filament, thus coated, is handled in known manner in the bristling of toothbrushes and hair brushes. By means of an automatic bristling machine it is fastened into place in the brush 3?? and forms full, straight, compact, neat Example No m n "Lorel" Herons III 0. 26 0. 25 W. 6

IV 0. 25 0. 6 99. 26 v i; as a" .7 I 0 .I '1. 5 3. 5 96. 0 v 'n 0.0 2. 0 96. 0

These are used in the same manner described in Example 11 and with similar results. Example IX.-'--A result similar to those of the preceding examples is obtained by the use of a solution of "0-18 alcohol" alone in octane, in concentrations between about0.5 and 5.0 but the coating substance. particularly if it has been applied in higher concentrations, tends under some circumstances to flake off of the finished brushes. Acetone or hexane maybe used instead of octane.

Example 'X.A similar result is obtained through the use of a solution of Lorol" alone in hexane, in concentrations within the same range, but inA-general the amount of Lorol" required is appreciably greater than the amount of "0-18 alcohol; required with the same filament.

Example XL-Insteadof being passed through a solution in continuous form, the filament is made up into loose hanks, which are dipped into the solution, drained and dried.

Example XIL-The filament in the form of.

non-solvent, to form on the filament a coating thereof, from which the liquid is then evaporated to leave a coating of the desired substance.

Example XIV.The following ingredients are passed through a colloid mill:

"Lorol 0.42 (3-18 alcohol 0.42 Sodium cetyl sulfate 0.05

Water. 99.11

The resulting dispersion is applied to the surface of the bristling filament of Example 11/ The filament is drained and thoroughly dried and used in automatic bristling equipment.

Example XV.A dispersion of:

Cetyl alcohol 0.80 Sodium cetyl sulfate 0.15 Water 99.05

is used as in the foregoing example.

I Sodium Sodium odium Exn n C-lB" Cetyl y ample Lmol alcohol alcohol fi'fg 3mg: \okme XVI... 2. I. 0 0. 3 96. 7 XVII 2. 5 U. 3 97. 2 XVIII l U 1. 0 l). 5 97. 5

X 0. 6 0. 4 0. 1 I. 98. 9 XX 0. 5 O. 5 l. 0 98. 0 XXI". 0.3 0.2 u U. 1 99.4

The above dispersions are used as in the preced ing examples.

Itwill be understood that the above examples are merely illustrative and that the invention is broadly applicable to bristling filaments made from any of the considerable number of individuals included in the general category of synthetic fiber-forming polymeric amides. In general, any of these may be used in the form of a bristling filament but, of course, certain of them, including those specifically mentioned in the examples herein are, for reasons of cost or characteristics, better suited and hence more widely used than others.

From the foregoing examples it is evident that the coating may be applied to the filament while the latter is in continuous strands, or in hanks, or in bundles. When the coating is applied, as preferred, in a liquid medium, its concentration therein will be adjusted to the conditions of operation, such as the condition of aggregation of the filament, the thoroughnesswith which the wet filament is drained, et cetera, between a minimum which will leave an inadequate coating of the material and a maximum which will leave a coating so heavy as to be wasteful or unsightly. In a solvent, the percentage of coating material will lie usually between about 0.5 and 5, and pref erably between about 2 and 3. In a non-solvent the percentage will usually be between about 0.5 and 3, and preferably around 1.

- When the coating is applied in an aqueous vehicle it is essential that the filament be held straight during the subsequent drying, so that it will not acquire a permanent distortion.

The present invention provides means .of ensuring the proper behavior of filaments of synthetic polymeric amides in the operations of bristling brushes, and thereby facilitates not only this operation but also the subsequent operations of trimming and finishing the tufts of filament. Correspondingly, it enhances the appearance and utility of brushes made from such filaments. It does not alter the stiffness of the filament nor introduce taste, odor, or toxic influence.

The manner in which the processof the present invention brings about the above mentioned advantages is not understood. There is no evidence that the coating makes the filament any more or any less slippery and, furthermore, it has been found that other substances of somewhat similar character are relatively or completely inefiective. Most nearly approaching the effectiveness of the alcohols of the present invention are fats such as glycerol trioleate but they are definitely inferior, for the purposes of the present invention, to the herein mentioned alcohols.

The coatings of the present invention neither increase nor decrease the sensitivity of the filament to water.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. In the manufacture of brushes with filament of'synthetic polymeric amides as bristles therein, the step of coating the said filament with a substance selected from the group comprising the straightchain alcohols containing even numbers of carbon atoms between 12 and 18, inclusive.

2. In the manufacture of brushes with filament of synthetic polymeric amides as bristles therein, the steps which comprise coating the said filament with a substance, selected from the group com prising the straight-chain alcohols containing even numbers of carbon atoms between 12 and 18, inclusive, contained in a liquid vehicle, and thereafter evaporating the said liquid vehicle from the surface thereof.

3. In the manufacture of brushes with filament of synthetic polymeric amides as bristles therein, the steps which comprise coating the said filament with a solution of a substance selected from the group comprising the straight-chain alcohols containing even numbers of carbon atoms be-' tween 12 and 18, inclusive, in a liquid solvent, and thereafter evaporating the said solvent from the surface thereof.

4. In the manufacture of brushes with filament of synthetic polymeric amides as bristles therein,

the steps which comprise coating the said filament with an emulsion of a substance selected from the group comprisin the straightechain alcohols containing even numbers of carbon atoms between 12 and 18, inclusive, in a liquid vehicle, and thereafter evaporating the said liquid vehicle from the surface thereof.

5. A bristling filament comprising a filament of a synthetic polymeric amide and a coating thereon of a substance selected from the group comprisingthe straight-chain alcohols containing even numbers of carbon atoms between 12 and 18, inclusive.

6. A brush comprising filament of a synthetic polymeric amide and a coating upon said filament of a substance selected from the group comprising the straight-chain alcohols containing even numbers of carbon atoms between 12 and 18, inclusive.

MAURICE L. MACHT. MALCOLM M. RENFREW. 

